1. Field of the Invention
The present invention relates to a tire forming method and apparatus wherein a tire member is conveyed axially out of the tire forming apparatus after it is bent over a tire forming drum.
2. Background Art
Generally, a tire member such as a carcass is wound on a tire forming drum, a pair of beads are fitted on the tire member, and the portions of the tire member, which extend outside the beads in the axial direction of the tire forming drum, are bent over around the beads, and the tire member thus bent around the beads is conveyed out of the apparatus to form a pneumatic tire.
When such tire portion is conventionally bent over, the portion is pushed and spread outwards in the radial direction of the tire forming drum by a bladder, for example, and a can is moved toward the axially middle part of the drum to push down the bladder to bend over the portion around the bead. When the bent-over tire member is conveyed axially, the diameter of an expansible and compressible conveyance ring is reduced to hold the tire member on the peripheral surface thereof, and the ring is then moved in the axial direction of the drum to convey the tire member axially away from the drum.
In a conventional method of bending over a portion of a tire member, a bladder disposed radially inside the portion is first expanded to push and spread the member portion in the radial direction of the tire member, and a can is then moved toward the axially middle part of a tire forming drum by an oil or air cylinder to push down the expanded bladder, so as to bend over the portion around a bead.
In another conventional method of bending over portion of a tire member, the portion is pushed and spread in the radial direction of the tire member by a first bladder, and a second bladder provided outside the first bladder in the axial direction of the tire member is expanded to push down the first bladder toward the axially middle part of a tire forming drum, so as to bend over the portion around a bead.
Since the bending-over of the tire member and the discharge of the tire member from the drum are performed by the can and the conveyance ring, respectively, it is difficult to control the bending-over and the axial discharge of the tire member. Since a waiting time is required to prevent the interference of the can and the ring, the efficiency of the formation of the pneumatic tire is low. Since the can and the ring need to be separately provided to achieve bending-over of the tire member and the axial discharge, the cost of equipment is high.
Since high-pressure oil or air needs to be supplied to the cylinder to drive the can in the former conventional method, the cost of equipment is high and the strength of the equipment needs to be high. If a bending over condition such as the length of the bent-over portion changes, the quality of the portion bent over becomes irregular.
Since high-pressure (6 to 7 kg/cm.sup.2) air needs to be supplied to the first and the second bladders in the latter conventional method, the cost of equipment is high. When a bending-over condition such as the length of the bent-over portion changes, the quality of the portion bent over becomes irregular. If the pressure in the first and the second bladders and the timing of the pressurization of the bladders become even slightly improper, the quality of the portion bent over drops.